1. Technical Field
The present invention relates to an electronic device and an altitude calculation method.
2. Related Art
A barometric altimeter for informing a user of a current altitude has been widely used in mountain climbing or the like. The barometric altimeter assumes a current altitude by applying an actually measured value of the atmospheric air pressure to a conversion expression (a height measurement expression) based on the fact that the atmospheric air pressure is low as an elevation of a spot becomes higher.
As is well known, parameters of the conversion expression are changed by the minute according to weather conditions, and thus, for example, it is necessary to perform calibration of barometric pressure and altitude measurement at a constant frequency such as every hour (or at a required timing).
Furthermore, herein, altitude measurement using a barometric pressure sensor will be referred to as “barometric pressure and altitude measurement”, and setting or adjustment of conversion properties (conversion parameters) of converting output of the barometric pressure sensor into an altitude will be suitably referred to as “calibration”.
In the calibration, an altitude of a spot where a user exists is used. For example, in U.S. Pat. No. 6,434,485, it is described that geography data including altitude information is stored in a memory, and acquires altitude information which corresponds to an altitude corresponding to a position determined by a GPS unit from the memory, and thus, calibration is performed.
However, in a case where calibration according to a variation in a barometric pressure is performed or a current altitude is calculated by using geography data, geography data which specifically covers a destination region of a user is required. For this reason, a data amount in geography data stored in a portable terminal device increases.